B3948

DTC B3948 or B3949

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.

DTC Descriptors
DTC B3948 02
- Left Front Turn Signal Circuit Short to Ground

DTC B3948 05
- Left Front Turn Signal Circuit Short to Battery or Open

DTC B3949 02
- Right Front Turn Signal Circuit Short to Ground

DTC B3949 05
- Right Front Turn Signal Circuit Short to Battery or Open

Diagnostic Fault Information





Circuit/System Description

Ground is applied at all times at G201 to the turn signal/multifunction switch. The turn signal lamps may only be activated with the ignition switch in the ON or START position. When the turn signal/multifunction switch is placed in either the TURN RIGHT or TURN LEFT position, ground is applied to the body control module (BCM) through either the right turn or left turn signal switch signal circuit. The BCM then applies a pulsating voltage to the front and rear turn signal lamps through their respective control circuits. Ground for the left front turn signal lamp is supplied at G101. Ground for the right front turn signal lamp is supplied at G102.

Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

B3948 02

This DTC will set when the BCM detects a short to ground in the LF turn signal control circuit.

B3948 05

This DTC will set when the BCM detects a short to voltage or an open in the LF turn signal control circuit.

B3949 02

This DTC will set when the BCM detects a short to ground in the RF turn signal control circuit.

B3949 05

This DTC will set when the BCM detects a short to voltage or an open in the RF turn signal control circuit.

Actions Taken When the DTC Sets

B3948 02

When this DTC is present, the LF turn signal lamp will not operate.

B3948 05

When this DTC is present, the LF turn signal lamp will be ON at all times for a short to voltage condition. For an open condition, the LF turn signal lamp will be inoperative.

B3949 02

When this DTC is present, the RF turn signal lamp will not operate.

B3949 05

When this DTC is present, the RF turn signal lamp will be ON at all times for a short to voltage condition. For an open condition, the RF turn signal lamp will be inoperative.

Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.
* A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Diagnostic Aids

* Check the LF turn signal bulb. If the bulb is open, DTC B3948 05 will set as current only.
* Check the RF turn signal bulb. If the bulb is open, DTC B3949 05 will set as current only.

Reference Information
Schematic Reference

Exterior Lights Schematics (Exterior Lights Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate front turn signal lamp.
2. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal C and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit terminal A and ground.
4. Command the appropriate front Turn Lamp ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the appropriate turn signal lamp assembly.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Front Turn Signal Lamp Bulb Replacement (Front Turn Signal Lamp Bulb Replacement)
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming